Comments on Probe-Excited Oblique Ion-Acoustic Waves in a Multidipole Plasma Device

Low-frequency noise (fci < f < fpi) excited by positively biased probes of various diameters near the magnets in a multidipole plasma device is investigated. It is concluded that the noise is due to the excitation of oblique ion-acoustic waves, i.e., the electrostatic ion-cyclotron waves in the low field limit propagating at large angles to the magnetic field.